Recently, a transmission device responding to an Optical Transport Network (OTN) or the like has been provided as a transmission device (hereinafter, also called “node”) designed for telecommunications carriers. The telecommunication carriers are requested to build a network capable of continuously providing service by preparing a plurality of redundant paths (hereinafter, also called “routes”) and using a protection path bypassing a working path in order to ensure service availability even if the working path becomes incapable of communication caused by a failure. The telecommunication carriers are also requested to build a network with fewer facilities in order to suppress service providing price.
A method of building the network responding to the request includes, for example, a shared mesh restoration method. The shared mesh restoration method is a method of sharing a bandwidth with protection paths, so that resources used to restore the failure can be reduced and high service availability can be achieved with low cost.
An operation of the shared mesh restoration will be explained with reference to, for example, FIG. 12 and FIG. 13. FIG. 12 and FIG. 13 are diagrams for explaining the shared mesh restoration as existing technology.
As illustrated in FIG. 12, a network 1a used for explaining the conventional shared mesh restoration represents a network so that 11 nodes 10 including nodes 10A to 10K are connected to each other via 12 links 50A to 50L. A first working path P10 is set on a route of the nodes 10A, 10B, 10C, and 10D in the network 1a. In addition, a route of the nodes 10A, 10E, 10F, 10G, and 10D is assumed to be set as a first protection path P11 corresponding to the first working path P10.
A second working path P20 is set on a route of the nodes 10H, 10I, 10J, and 10K. In addition, a route of the nodes 10H, 10E, 10F, 10G, and 10K is assumed to be set as a second protection path P21 corresponding to the second working path P20.
FIG. 12 represents a state before a failure occurs. For the first working path P10 and the second working path P20, a bandwidth requested by a signaling message sent from each HE node (head node) along the respective paths is ensured. For example, an HE node (head node) of the first working path P10 is set as the node 10A, and an HE node (head node) of the second working path P20 is set as the node 10H. Settings for data plane including setting of input/output interfaces and setting of cross connection between the interfaces or the like are performed by the signaling messages, and it is thereby ready to flow user traffic.
In the network 1a, the first working path P10 and the second working path P20 pass through different nodes and different links respectively, and therefore the first working path P10 and the second working path P20 are not simultaneously affected by a single link failure or a single node failure. In this case, the shared mesh restoration allows the first protection path P11 and the second protection path P21 to share a bandwidth used thereby, and it is thereby achieved to provide economical protection paths.
Signaling messages for the first protection path P11 and the second protection path P21 are transmitted along the routes of the first protection path P11 and the second protection path P21 from the HE nodes respectively. The HE node (head node) of the first protection path P11 is the same as the HE node (head node) of the first working path P10, and the HE node (head node) of the second protection path P21 is the same as the HE node (head node) of the second working path P20. Pieces of path information of the first working path P10 and the second working path P20 are included in the signaling messages for the first protection path P11 and the second protection path P21 respectively. Therefore, because the nodes 10E, 10F, and 10G can know that the first working path P10 and the second working path P20 pass through the different nodes and links respectively, it can be determined that the bandwidth of the first protection path P11 and the second protection path P21 may be shared therewith.
Because the bandwidth of the first protection path P11 and the second protection path P21 is shared, the bandwidth requested by signaling is reserved on the routes along the protection paths, but the settings for the data plane including setting of input and output interfaces and setting of cross connection between the interfaces are not performed. The reason is that the settings for the data plane is not input because whether the shared bandwidth is used by the first protection path P11 or by the second protection path P21 is not determined before occurrence of a failure.
FIG. 13 represents a case where a failure occurs in the link 50L between the nodes 10J and 10K in the network of FIG. 12. The second working path P20 is affected by the failure, and therefore the failure information is notified to the node 10H being the head node of the second working path P20. When receiving the notification, the node 10H starts activation processing for switching communication of the second working path P20 to that of the second protection path P21.
As explained above, the bandwidth for the second protection path P21 is reserved, but the setting of input/output interfaces on the route of the second protection path P21 and the setting of cross connection between the interfaces are not finished, and therefore these settings need to be performed before the switching. To perform the settings, the node 10H transmits a signaling message requesting activation of the second protection path P21. When receiving the signaling message, the nodes 10H, 10E, 10F, 10G, and 10K along the second protection path P21 perform setting of the input/output interfaces and setting of the cross connection between the interfaces so that the second protection path P21 uses the bandwidth reserved for the second protection path P21 for share. When flowing user traffic is prepared on the second protection path P21 through the procedure, the nodes 10H and 10K restore the service by performing the setting so as to flow the user traffic via the second protection path P21.
Patent Literature 1: Japanese Laid-open Patent Publication No. 2007-14032
As explained in the existing technology, in the shared mesh restoration, signaling to activate a protection path is performed after the failure occurs, a data plane unit is set by each of the nodes on the protection path, and then the activation is performed. Consequently, even if a plurality of protection paths are to be activated, the activation is independently performed for each of the protection paths. Therefore, it may take time before the switching to all the protection paths is finished after the signaling is performed.
A case where it may take time before the switching to all the protection paths is finished after the signaling is performed will be explained below with reference to FIG. 14, FIG. 15, and FIG. 16. FIG. 14 and FIG. 15 are explanatory diagrams for explaining the shared mesh restoration according to the existing technology. FIG. 16 is a ladder chart exemplifying a case of performing switching based on the existing technology.
A network 1b of FIG. 14 is configured to add a link 50M between the nodes 10F and 10J, a third working path P30, and a third protection path P31 to the network 1a of FIG. 12 which is referred to for the explanation of the existing technology. In other words, the third working path P30 having a route of the nodes 10J and 10K is set in addition to the first working path P10 and the second working path P20. Moreover, the third protection path P31 having a route of the nodes 10J, 10F, 10G, and 10K is set in addition to the first protection path P11 and the second protection path P21.
Signaling messages for the third working path P30 and the third protection path P31 are transmitted along the paths of the third working path P30 and the third protection path P31 from the HE nodes (head nodes) respectively. The HE node (head node) of the third working path P30 is the same as that of the third protection path P31, and is assumed to be, for example, the node 10J.
Pieces of path information of the first working path P10, the second working path P20, and the third working path P30 are included in the signaling messages for the first protection path P11, the second protection path P21, and the third protection path P31 respectively. The first working path P10 and the second working path P20 pass through different nodes and links based on the path information included in the signaling messages, and therefore the corresponding first protection path P11 and the second protection path P21 share the bandwidth. The second working path P20 and the third working path P30 share the nodes and the links, and therefore the second protection path P21 and the third protection path P31 do not share the bandwidth.
FIG. 15 represents a case where a failure occurs in the link 50L between the nodes 10J and 10K in the network of FIG. 14. The second working path P20 and the third working path P30 are affected by the failure, and therefore the failure information is notified to the respective HE nodes (head nodes) of the second working path P20 and the third working path P30. When receiving the notification, the node 10H starts transmission of the signaling message for activation of the second protection path P21. Likewise, the node 10J starts activation of the third protection path P31.
FIG. 16 is a ladder chart exemplifying a case of activating the second protection path P21 and the third protection path P31 using the conventional technology. Specifically, FIG. 16 is a diagram for explaining how the activation is performed when the failure illustrated in FIG. 15 occurs.
As illustrated in FIG. 16, when the second protection path P21 and the third protection path P31 are activated by using the conventional technology, the failure notification for the second working path P20 is notified to the HE node (head node) 10H of the second working path P20, and then signaling is performed in order to activate the second protection path P21 along the route of the second protection path P21 from the node 10H. Likewise, the failure notification for the third working path P30 is notified to the HE node (head node) 10J of the third working path P30, and then signaling is performed in order to activate the third protection path P31 along the route of the third protection path P31 from the node 10J. The activation of the second protection path P21 and that of the third protection path P31 are performed independently by the signaling. Therefore, the second protection path P21 is not activated based on the prediction that the failure of the link 50L occurs on the same route, and the time at which the switching to the second protection path P21 is complete becomes time t1.
In one aspect, it is to provide a transmission device and an activation method capable of shortening the time until the completion of switching when a plurality of protection paths are activated in the shared mesh restoration, and a network designing device and a network designing method for effectively using the method.